1. Field of the Invention
The present invention relates to a liquid crystal dispensing system, and more particularly, to a liquid crystal dispensing system capable of preventing an inferiority of a liquid crystal display device by dispensing a precise amount of liquid crystal onto a substrate and a method of dispensing liquid crystal using the same.
2. Description of the Related Art
Recently, various portable electric devices, such as mobile phones, personal digital assistant (PDA), and note book computers, have been developed because of their small size, light weight, and power-efficient operations. Accordingly, flat panel display devices, such as liquid crystal displays (LCDs), plasma display panels (PDPs), field emission displays (FEDs), and vacuum fluorescent displays (VFDs), have been developed. Of these flat panel display devices, the LCDs are currently mass produced because of their simple driving scheme and superior image quality.
FIG. 1 is a cross sectional view of an LCD device according to the related art. In FIG. 1, an LCD device 1 comprises a lower substrate 5, an upper substrate 3, and a liquid crystal layer 7 formed therebetween. The lower substrate 5 is a driving device array substrate, and includes a plurality of pixels (not shown) and a driving device, such as a thin film transistor (TFT), formed on each pixel. The upper substrate 3 is a color filter substrate, and includes a color filter layer for reproducing real color. In addition, a pixel electrode and a common electrode are formed on the lower substrate 5 and the upper substrate 3, respectively. An alignment layer is formed on both the lower and upper substrates 5 and 3 to align liquid crystal molecules of the liquid crystal layer 7. The lower substrate 5 and the upper substrate 3 are attached along a perimeter by a sealant 9, and the liquid crystal 7 is confined within the perimeter. In operation, the liquid crystal molecules of the liquid crystal layer 7 are reoriented by the driving device formed on the lower substrate 5 to control amounts of light transmitted through the liquid crystal layer 7, thereby displaying an image.
FIG. 2 is a flow chart of a fabrication method for an LCD device according to the related art. In FIG. 2, a fabrication method includes three sub-processes for manufacturing an LCD device: a driving device array substrate process for forming the driving device on the lower substrate 5; a color filter substrate process for forming the color filter on the upper substrate 3; and a cell process.
In Step S101, a plurality of gate lines and data lines are formed on the lower substrate 5 to define a pixel area by the driving device array process, and the thin film transistor connected to both the gate line and the data line is formed on the each pixel area. In addition, a pixel electrode, which is to be connected to the thin film transistor to drive the liquid crystal layer according to a signal applied through the thin film transistor, is formed by the driving device array process. In Step S104, R, G, and B color filter layers for reproducing the color and a common electrode are formed on the upper substrate 3 by the color filter process.
In Steps S102 and S105, alignment layers are formed on the lower substrate 5 and the upper substrate 3. Then, the alignment layers are individually rubbed to induce surface anchoring (i.e. a pretilt angle and alignment direction) for the liquid crystal molecules of the liquid crystal layer 7. In Step S103, a spacer is dispersed onto the lower substrate 5 for maintaining a uniform cell gap between the lower and upper substrates 5 and 3. In Step S106, a sealant is printed along outer portions of the upper substrate 3.
In Step S107, the lower and upper substrates 5 and 3 are assembled together by compression. The lower substrate 5 and the upper substrate 3 are both made of glass substrates, and include a plurality of unit panel areas on which the driving device and the color filter layer are formed. In Step S108, the assembled upper and lower glass substrates 5 and 3 are cut into unit panels. In Step S109, liquid crystal material is injected into the gap formed between the upper and lower substrates 5 and 3 of the unit panels through a liquid crystal injection hole. The filled unit panel is completed by encapsulating the liquid crystal injection hole. In Step S110, the filled and sealed unit panel is tested.
FIG. 3 is a schematic view of a liquid crystal injection system for fabricating an LCD device according to the related art. In FIG. 3, a container 12 in which liquid crystal material 14 is contained is placed in a vacuum chamber 10, and the liquid crystal display panel 1 is located at an upper side of the container 12. Then, the vacuum chamber 10 is connected to a vacuum pump (not shown) to maintain a predetermined vacuum/pressure state within the vacuum chamber 10. In addition, a liquid crystal display panel moving device (not shown) is installed in the vacuum chamber 10 to move the liquid crystal display panel 1 from the upper side of the container 12 to a surface of the liquid crystal material 14, thereby contacting an injection hole 16 of the liquid crystal display panel 1 to the liquid crystal material 14. Accordingly, this method is commonly called as a liquid crystal dipping injection method.
When the vacuum/pressure level within the chamber 10 is decreased by an inflow of nitrogen gas (N2) into the vacuum chamber 10 in the state that the injection hole 16 of the liquid crystal display panel 1 contacts the surface of the liquid crystal material 14, the liquid crystal material 14 is injected into the liquid crystal display panel 1 through the injection hole 16 by the pressure differential between the vacuum/pressure level within the liquid crystal display panel 1 and the pressure/level within the vacuum chamber 10. After the liquid crystal material 14 is completely filled into the liquid crystal display panel 1, the injection hole 16 is sealed by a sealant to seal the liquid crystal material 14 within the liquid crystal display panel 1. Accordingly, this method is called as a vacuum injection method.
However, there are several problems with both the liquid crystal dipping injection method and/or vacuum injection method. First, an overall time for injection of the liquid crystal material 14 into the panel 1 is relatively long for either method. In general, a gap thickness between the driving device array substrate and the color filter substrate in the liquid crystal display panel 1 is relatively narrow, i.e., a few micrometers. Accordingly, a relatively small amount of liquid crystal material 14 is injected into the liquid crystal display panel 1 per unit time. For example, it takes about 8 hours to completely inject the liquid crystal material 14 into a 15-inch liquid crystal display panel, and thus, fabricating efficiency is decreased. Second, consumption of the liquid crystal material 14 during the liquid crystal injection method is large. Only a small amount of the liquid crystal material 14 in the container 12 is actually injected into the liquid crystal display panel 1. Accordingly, during loading of the liquid crystal display panel 1 into the vacuum chamber 10, the unused liquid crystal material 14 is exposed to atmosphere or to certain gases, thereby contaminating the liquid crystal material 14. Thus, any remaining liquid crystal material 14 must be discarded after the injection of the liquid crystal material 14 into a plurality of liquid crystal display panels 1, thereby increasing fabricating costs.